Collision course
by lizzy2077
Summary: Charlie attempts to help Don and his team stop a string of bombings in the L.A. area. His work is made more difficult when he is surprised by someone from his past-
1. Default Chapter

_I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only._

Charlie and Amita were still discussing the details of their latest contribution to Don's case as they took the elevator upstairs. Charlie felt it wasn't ready yet, but Amita felt they couldn't do any better with what they'd been given for information, and they were under a lot of pressure to produce something quickly. Don met them at the door and they all walked to the bullpen together. David and Terry were already waiting there.

"Okay Charlie, what have you got for us?"

Charlie and Amita exchanged looks before he spoke. "Well, I'll give you what we've got, but I don't know how much it will help."

Terry gave Charlie an encouraging smile. "Anything will be a help at this point."

Amita connected Charlie's laptop up to the projector as Charlie began to walk everyone through the calculations.

"Based on the data you provided, this is what we've come up with…" Don's team was currently trying to find a pattern, and from that a source, for multiple bombings around the Los Angeles area. Six people were already dead, and there were dozens more in the hospital. Although the bombs were relatively small in scale, it had thrown the city into somewhat of a panic. The case was further compounded by the fact that it was different locations and different types of sites every time. The first explosion had been in a supermarket, but the last one had been at a highway rest stop. Everyone was looking at the map Charlie had generated, trying to follow his line of logic.

Don wrinkled his brow as he stared at the projected map. "Talk me through this again, Charlie, because I just don't see what you're seeing."

Charlie walked up to the projection screen and starting pointing to the indicators as he went over his calculations again. "The greatest concentration seems to be here, as far as number, but the more severe cases have been concentrated in this area farther south. So, after quantifying the data, we're saying your hot zone is here."

"That's a pretty big hot zone, Charlie."

"I know." Charlie was staring at the screen too, looking disappointed with his own work.

"How accurate do you think it is?"

"It's about 78. I couldn't really get it any better than that with the numbers we have."

Don sighed and turned back to the case folders. "There's no way we can clear an area like that ourselves. I'd have to take every man off every other job they're doing, and even then…"

Charlie looked dejectedly back at the group. "I'm sorry, guys…"

"It's not your fault, man; it's just this damn case! We've got some psycho out there terrorizing the city and we've got nothing to go on."

"Look, maybe it would be better at this point if I just went back to looking for clues in the pattern instead of trying to find the source."

"Whatever you think will help."

"You know, Don, we don't know that this is one guy. I still think we could be looking at a group," Terry reminded her partner gently.

Their conversation was interrupted by the entrance of Assistant Director Merrick. "Excuse me, Eppes…"

Both Charlie and Don turned to look at Merrick. "_Agent_ Eppes. I want you to go downstairs and get that new special ops training director. Have her give you a hand on this."

"Sir?"

"She's former CIA, Eppes, she's worked cases like this. Run it by her, see what she has to say."

"Yes, sir."

As soon as he left the room, Don rolled his eyes, clearly unhappy about having to get a second opinion. Terry, sensing Don's frustration, tried to be positive. "Look, maybe a fresh set of eyes would help on this."

"Right." Don gave Terry a 'don't try to make me feel better about this' look before heading out the door.

Charlie and Amita immediately got behind their laptops and went to work on their calculations again. Terry and David were discussing their other leads for solving the case.

"Okay, have we heard anything back on the security team for the locations?" Terry was rummaging through papers on the table.

"Nothing yet, unless they called Don."

"No, Don would have told us. Where do we stand with the bomb reconstruction?"

"Miller said he would have more concrete findings within the next few hours."

Terry let out a sigh. "There's got to be something we're missing here—some clue, something."

"Nobody's sleeping on this one Terry. We've got everybody working around the clock."

"I know, but maybe that's part of the problem. We're all sitting too close to the screen to see the big picture."

Just then, Don re-entered the room, followed by a dark-haired woman.

"Everybody, this is Agent Cruz. Cruz, this is my partner, Terry Lake, and that's David Sinclair. Over there is my brother, Ch-"

"Charlie?"

Charlie's head snapped up at hearing his name. His eyes widened as they fell on the woman standing in the doorway. His face drained of all color. "Isabel…"


	2. Chapter 2

_I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only._

**February 2002, CalSci**

"Well, Professor Eppes, you can officially consider me impressed. That was quite a class."

Charlie turned to see a woman in a black pantsuit walking toward him. He hadn't noticed anyone still in the room after his class, and she definitely didn't look like one of his students.

"Um, thank you. Do I know you?"

"We spoke on the phone. I'm Isabel Cruz; it's a pleasure to meet you." She extended her hand and he shook it.

"Right! I'm sorry, you're with the agency."

"Yes, some days I'm sorry too." She smiled broadly at him.

"Oh! No, I didn't mean it like that! I meant I'm sorry I didn't realize who…" She cut him off before he could stick his foot any farther in his mouth.

"It's okay. I know what you meant to say. I was just joking, sort of."

"Right." This was not off to the kind of start he liked. "Well, we can go back to my work space to discuss your project if you want."

"Of course. Lead the way, professor. Or do you prefer to be called doctor?"

"Actually, you can just call me Charlie."

"Okay, Charlie." The way that she said his name with her slight accent made it sound unlike any way he'd heard his name before, but he liked it.

Charlie had done a few consulting jobs for different government agencies before, but in the first five minutes of meeting Agent Cruz, he knew she was unlike any government employee he'd ever met—his brother included. If he had met her on the street he would have never guessed she had such a serious job. In the hour they'd already been in his office, if you could call it that, they'd barely even talked about her project. She seemed to be far more interested in learning about Charlie and his work than she was in her own. He couldn't decide if she was interviewing him, or if she was just genuinely interested.

"So do you live around here?"

"My family's house is a couple of miles away."

"That's good. The traffic is terrible around here."

"Oh, I don't drive here anyway. I use my bike." It was one of the only times Charlie remembered feeling completely self-conscious saying that.

"Really? That's great exercise!"

"Yeah." He hoped he said that enthusiastically enough that she would actually think that's why he did it.

"And your brother works for the FBI, yes?"

"Yeah, he actually heads up the Albuquerque office now."

"Impressive."

"He's doing really well for himself, but I don't get to see him that much."

"You don't want to ride your bike all that way to go visit?" She grinned at him and Charlie could tell he clearly wasn't going to get anything by her. It was time to change the subject.

"So, you didn't say much about this work on the phone. What exactly does this project entail that you need my help?"

Isabel smiled, looking intently at Charlie. He was wondering if he'd offended her by wanting to get to work, but he desperately wanted to get to a conversation where he wouldn't feel like such a moron.

"The project." She pulled a few file folders from the briefcase she carried with her. "This isn't everything, mind you, but it should give you an idea what we're looking for."

Charlie scanned over the material she put in front of him as she explained what she needed him to do. "We need to take a lot of data of this nature," and she pointed to the file folder Charlie was currently going over, "and hopefully find a way to make it lead us to a source. Just so you know, I have about four file boxes full of that."

"You have four boxes full of these?" Charlie held up one of the papers from the folder.

"Yes."

Charlie raised his eyebrows as he continued scanning the pages. "This is a pretty big job, then."

"Yes."

"Well, that could be good. More data gives better results, but sometimes more data is just that…more data."

"Yes."

When Isabel hadn't spoken again in several minutes, Charlie looked up. It appeared she'd just been watching him go over the files, which made him a little uncomfortable. For someone who stood in front of an entire classroom of students every day, he didn't like being watched. Especially when he had the distinct feeling it was more like being studied.

"You know, it would help if I knew exactly what kind of data I'm looking at."

"It would help or it is necessary?" Charlie stared at her with a slightly puzzled expression. Didn't she know it was necessary?

"Because if it's necessary then I can tell you, but then I would have to kill you when you're finished."

She said it so calmly and evenly that Charlie had no idea if she was being serious or not. He swallowed hard, not taking his eyes off her. Suddenly, she smiled and laughed a little.

"I'm joking with you. It's a joke."

"Right, of course." He laughed nervously as he wondered why he was such an idiot with this woman.

"Seriously though, do you _really_ need to know what it is?"

"It's going to be hard to turn it into anything if I don't know what I'm working with."

"It's all quantified into numbers though. This is what you do; you work with numbers."

"Yes, but numbers in context. These numbers are all out of context. If you're going to leave me with four boxes full of data, then I'm not sure how much I can do for you."

She smiled and laughed again. "Oh, well if that's what you're worried about is me just dropping all of this on you and taking off, don't be. I'm not leaving this information. I am staying and working on it with you."

"You're going to run through all of this data with me?" Charlie was unable to hide his surprise. No one had ever actually wanted to work _with_ him on a consulting case. They always just wanted him to work _for_ them. "Do you know how long this could take?"

"Yes, I am and yes, I do. Unless you prefer to work alone, and then maybe we do have a problem."

"No, there's no problem." There was definitely no problem.


	3. Chapter 3

_I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only._

**Present**

Charlie and Isabel just stared at each other while everyone around them was left to wonder. Don was the only one who felt comfortable asking the obvious, "You two know each other?"

Neither of them responded for a moment, then Isabel blinked and looked over at Don. "Charlie and I worked together on a case a few years ago."

Charlie said nothing, only sat there and stared at Isabel. "I'm sorry, but would you excuse us for a moment? Charlie, can I speak to you?"

Charlie nodded and got up to leave, but still said nothing.

They left the room, walking around the corner where they would be out of ear- and eye-shot of everyone else.

Charlie opened his mouth and then closed it a couple of times as he was trying to figure out what to say. He'd nearly passed out when he looked up and saw her standing there. After all, he hadn't seen or heard from her in two and a half years.

"Charlie, I'm sorry, I realize this is a shock."

Suddenly, Charlie found his voice. "A shock? Is that what you call it? For all I knew, you were dead!" He said the last few words much louder than the first and several people began staring in their direction.

Isabel quickly looked around and pulled him into an empty conference room. "Charlie, please, we can't do this here."

He rubbed his eyes and ran his hands down his face, attempting to collect his thoughts. "Isa, I…"

"I promise; we can talk later. This is just not the place for this conversation."

"How am I supposed to go back in there and work with you right now?"

"I don't…I don't know."

"How could you…how can you be here and not have at least called me?"

"Charlie, please try to understand…"

"I've been trying to understand for the past two and a half years!"

Isabel closed her eyes and took a deep breath. "We have to go back in there and get to work, Charlie. People's lives are at stake and there are bigger things that need our attention right now."

She watched as the emotion left his face. "You're right. This is more important than you and I."

"Charlie, that's not-," but he was already out the door. "-fair."

Letting out a heavy sigh, Isabel followed him back into the other room.

Everyone turned and looked as Charlie re-entered, Isabel close behind. Don couldn't remember the last time he saw his brother with that look on his face. It was the only look that when Charlie had it, Don stayed away. He hadn't seen it in years, and if his curiosity was piqued before, it was killing him now. Who was this woman who had such a profound, albeit negative, effect on his brother?

Charlie sat back down at his computer, not saying a word. Amita tried to catch his eye with no success. He wouldn't look at anyone.

Isabel did her best to maintain her calm composure, as though her life hadn't just experienced a major upheaval. "I apologize for the interruption, Agent Eppes, you were going to go over the rest of your information with me?"

Don snuck a quick glance at Charlie, who was trying desperately to get back to work on his laptop. Don knew his brother well enough to know he wasn't getting anything done right now. He had about a hundred questions he would have liked to ask this woman, but this was not the time. They needed to get down to business.

"Yes, I'll show you what we're working on over here." Don and Isabel walked over to the far wall as he went over the maps and more of the details of the case.

Terry fidgeted in her seat. Being who and what she was, it was her job to be very in tune with those around her, and right now it was making her very uncomfortable. The tension was so thick in the room you could cut it. She'd grown rather fond of Charlie in the time they'd worked together and found she often thought of him like he was her own brother. She didn't like seeing him so upset. It had been very obvious to her the moment that the two saw each other that there was significant history between them. She was reminded of the time Kim and Don saw each other. Although she still didn't know all the details of that little piece of Don's history, she knew enough to know it had been serious. She wondered just how involved Charlie and Isabel had gotten while they worked on that case.

Lost in her thoughts, Terry jumped a little when Charlie tapped her on the shoulder. He forced a smile when she turned and looked at him, but she wasn't buying it for a second.

"Look, I left some of my papers back at school. I'm going to need them if we're going to go back over all of our work. So we're going to just work over there. I'll call Don if we come up with anything useful." He nodded toward his brother and added, "I don't want to interrupt him."

"Okay, Charlie, I'll let him know." Don was deep in conversation with Isabel and didn't seem to notice Charlie and Amita leaving.

Terry watched them walk out, knowing damn well that Charlie hadn't left anything behind at school.

When the door closed behind them, Don turned around and quickly scanned the room. "Where'd Charlie go?"

As innocently as she could, Terry replied, "He and Amita left some papers they needed at school so they're going to finish up there." She saw from the flash in Isabel's eyes that she knew it was a flimsy excuse too.

Don, however, didn't seem to care what it was. He was annoyed. "Did he say he'd be back?"

"No, he said he'd call you if they came up with anything…'useful'."

Don turned back to Isabel. "Well, until I get some updates, I guess that's as much as I can give you right now."

"That's fine, don't worry about it. If you don't mind, I'd like to take some of these case files with me to look over. I have a meeting I need to get to." She glanced at her wristwatch. "I can bring them back to you first thing tomorrow, hopefully with some ideas."

"That's fine, take what you need."

Isabel grabbed the stack of files Don had briefly run through with her. "I'll see you tomorrow then."

"Yeah, thanks."

As soon as she had walked out the door, Don and Terry exchanged meaningful looks.

"Alright, Terry, professional opinion: what the hell was that?"

"I can only speculate. I think you're going to have to go to the source if you want to know the truth."

"Yeah, _that's_ a conversation I'm looking forward to." Don hadn't forgotten the whole incident with Charlie and Kim, and he was dreading having to pry into his brother's history. He had a few guesses at the story, based on his own experiences, but he had a hard time believing Charlie and Isabel had ever been…involved.

He sat down with Terry and David and got back to work. As important as his brother was, he couldn't afford to be distracted by him right now.

When Charlie and Amita got to her car he said quietly, "Would you mind just dropping me off at my house? I don't think I can work on this anymore today."

"Um, okay."

"Thanks." Charlie got in the passenger's seat and closed his eyes. He was thankful Amita wasn't asking any questions; though he was pretty sure she probably wanted to.

They drove in silence to his house, Charlie feeling like someone had just punched him in the stomach. He still couldn't quite believe that he'd just seen Isabel. His life had just started to get back to some semblance of normal, and there she was.

"Charlie?"

Charlie opened his eyes, realizing they were parked outside his house. He grabbed his things from the backseat and got out of the car.

"Thanks Amita, I'll see you tomorrow."

"Sure."

He started to walk up the steps to his house. "Hey, Charlie!"

He turned around to look at Amita. "Yeah?"

"Are you okay?"

"I'll be fine. Don't worry about it. See you tomorrow."

Amita eyed him suspiciously, but nodded and drove away.

Charlie walked in the door; his father was sitting in a chair reading a book.

"Hey, Charlie."

"Hey, dad."

"You're home early."

"Yeah, well, work didn't go that well today. I figured I'd come back here and sort it out."

"Oh, sorry to hear that. Is your brother coming for dinner?"

Charlie realized he'd forgotten to ask Don, but then he thought about what had just happened at the office. "Yeah, he'll be here."

Alan watched as his youngest son dragged his bag upstairs. He wondered just how bad his day had been. He hadn't seen him look that down since…well, in a long time.


	4. Chapter 4

_I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only._

**Flashback chapter**

**March 2002**

"Seriously Charlie, I need a break. You must need a break."

Charlie only continued writing on the board.

"Earth to Eppes, come in Eppes."

Again there was no answer, only the sound of the marker squeaking against the board.

Sighing, Isabel got up from her chair and put herself in between Charlie and the board. "¿Hola? I'm speaking to you."

Trying his best to work around her, Charlie only replied, "I'm working."

Isabel grabbed the marker out of his hand, effectively making sure she had his full attention before speaking again.

"You—_we_—need a break."

"I don't need a break." Charlie attempted unsuccessfully to get the marker back.

"Yes, you do."

"No, I don't."

"Yes, you…what am I saying? Charlie! You're taking a break."

Charlie opened his mouth to argue, but nothing came out. He was too tired to come up with anything, and he'd learned from experience that arguing with this woman was almost entirely futile. He flopped down into the nearest chair and rubbed his eyes. "What time is it?"

"It's time to eat."

"Seriously, what time is it?"

"It's 8:30, and it's seriously time to eat. What do you feel like?"

"A nap."

"For food, I mean."

"I don't really care."

"You want to order from the same place as last night?"

"Sure."

Isabel left Charlie alone in the room, presumably to go find a menu. He briefly considered getting back to work, but he realized he could barely bring his own writing into focus. These were the times when he wished he didn't need sleep. He knew he could put it together if he just kept at it a little longer. He turned his chair around and put his head down on the table. He only needed to rest his eyes a minute.

Over the past few weeks, he'd been working with Isabel a lot, probably investing more time than he should. He had tests to correct and other calculations to do, but every time he had a few hours to work, he found himself coming here. They had taken over a small office space in one of the government buildings downtown. It was a little cramped between the furniture and all of his boards, but it worked for them. Charlie kept telling himself that the challenging nature of the project was what was keeping him up at night, making him lose sleep. It was the work that kept him coming back at all hours. Yet sometimes he couldn't silence the voice in the back of his head, and he couldn't ignore that momentary sinking sensation in his stomach when Isabel looked in his eyes.

Isabel returned with the menu in one hand, her cell phone in the other, only to find Charlie sleeping in a chair, his back rising and falling slowly. She thought about letting him be, but he had to get back home within an hour to avoid suspicions. They'd been working nearly a month without anyone at his work or home knowing about it, and she very much wanted to keep it that way. He just looked so peaceful, and she knew he desperately needed the sleep.

"Charlie." She whispered, not wanting to startle him, but he didn't move.

"Charlie." She got a little closer, but still no response. Leaning in closer to him, she pushed a stray curl off his face. "Charlie."

He bolted upright and looked at her, startled. She smiled and tried not to laugh.

"Sorry, I know you need your sleep, but you can't do it here."

"Right, sorry. I just…"

"I know. Look, you eat first and then I'll take you home."

"Okay."

Isabel could see Charlie was fighting to keep his eyes open. "You know what? Screw it. Let's just stop at that diner a few blocks up and then I'll drive you back straight from there."

"I thought we were trying to avoid being seen together in public."

"Yes, I know I said that, but it's not like we're having some sordid affair! Besides, what are the odds anyone you know will be there at this time?

"Well, there are a lot of factors to consider…"

"Oh, for goodness sake Charlie, it's just an expression! I didn't want to know the _actual_ odds!"

Charlie smiled and Isabel laughed. "Come on," she said, "let's get the hell out of here for tonight."

Isabel tried to stifle a yawn as they walked to her car. "I can't believe I'm this exhausted and it's not even 9. That's beyond pathetic."

"I know what you mean. Actually," Charlie stopped walking suddenly, "would you mind if we just walked there? It might wake us up."

"Sure. We can just get the car afterwards."

They walked in relative silence for the first two blocks, until Isabel spoke.

"I hope you know, Charlie, that I really appreciate all of your help. You're really good at what you do."

Charlie didn't quite know what to say. Over the years, he'd become accustomed to people complimenting his work, but from Isabel it made him a little uncomfortable. "Um, thanks."

"I'm not trying to embarrass you or anything, but I've worked with a lot of other people in the course of my career with the CIA, and you're definitely on my short list of few to work with again. It's been my experience that people that possess your level of intelligence tend to think that they're better than everyone else around them, but I've never gotten that sense from you. You've got a great way of working with people and bringing them up to your level, and that's a gift just as much as your intelligence. I'm sure your students really appreciate it."

Charlie just smiled awkwardly and looked down at his shoes as he walked. He couldn't remember the last time anyone made him feel so…flattered. "You know, you're not like anyone I've ever worked with before either."

Isabel made a funny noise and said, "Now is that a good or a bad thing?"

"It's a good thing, definitely a good thing."

"Okay, well thank you then."

"You're welcome."

Charlie wanted to say something else, but as he was trying to formulate the words in his head, they had reached the diner. Once again, he let the feeling pass and said nothing.


	5. Chapter 5

_I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only._

**Present**

"Hello?" Don had entered the house, but no one appeared to be home.

"Hey, Donnie, how was work?" His father appeared from the kitchen.

"Actually, it's not going that great. I should still be there, but I need to talk to Charlie."

"You're not staying for dinner?"

"I can stay, just not for long." Alan could tell from the tense look on Don's face that something was really bothering him. He had a sneaking suspicion it wasn't just work.

"Your brother's upstairs." Don made a move toward the stairs, but his father continued. "He came in with a look worse than the one you're wearing. You want to tell me what's going on?"

"Honestly, dad, I don't know. And even if I did, it's probably not my place to say."

"So this is some problem of Charlie's."

"Yeah."

"Should I be concerned?"

"No, don't worry about it; I've got this one covered."

"Did you upset your brother?"

"No! Why do you always assume it's me?"

"Don't get all upset. And what are you talking about? I don't 'always assume it's you!' It's just that there aren't many people who can get under Charlie's skin enough to have that kind of effect."

"He looked pretty bad, huh?"

"About as bad as I've seen him since your mother died."

"Look, I've got an idea what this is about. Just let me go talk to him."

Alan gave his son an appraising look as though deciding whether or not that was really the best course of action. "Well, knowing him he hasn't eaten since breakfast so do me a favor and get him down here for dinner. I'll call you when it's ready."

"Thanks, dad."

Don headed upstairs, gathering his thoughts on the way. He hated nosing into Charlie's business but he didn't want to ignore what had happened either. As the big brother, Don always felt he needed to protect Charlie. Ever since they went to school together, protecting Charlie had included trying to shield him from the pain the opposite sex could inflict. Don still kicked himself for ever letting him go out with Alison, his first girlfriend, who ended up breaking his heart.

He walked in the solarium, but as he suspected, Charlie wasn't working on the case. All of his papers were still in his bag, even his laptop sat untouched. He was staring out the window at the back yard.

"Hey, buddy."

Charlie snapped around, obviously unaware Don had entered the room. "Hey, Don, I was just…" He walked over to the table and started pulling papers out of his bag.

Don walked over and put his hand on Charlie's arm. "Don't. I didn't come here about work."

Charlie turned his face to his brother's and Don took his hand away. "You want to tell me what happened today?"

Charlie did his best to make his face go blank. "I don't know what you're talking about."

"Oh, you're gonna have to do way better than that, Charlie. I think you forgot who you're talking to."

"I didn't forget." Charlie mustered a determined look and shrugged his shoulders. "I thought it was okay that we didn't talk about our past relationships with each other?"

Don saw that one coming a mile away, but he was ready for it. "So she _is_ an ex."

"Why does it matter? Why do you care?" He was clearly on the defensive, which was not where Don wanted him.

"Come on, Charlie, I thought we got past this."

Charlie shook his head and looked at the floor. "I know; I thought we did too."

"If you really don't want to talk about it, then say so; just don't lie to me about it."

Charlie let out a deep breath and his shoulders sagged. He threw himself down in the armchair by the window.

"It's a long story."

"They always are." They exchanged half-smiles before Charlie continued.

He took a deep breath and let it out sharply. "You already know we met on a case. It was about three years ago. We spent a lot of time together, working on it. She just… I'd never met anyone like her." Charlie turned and stared out the window. "One day, things just changed. Then one thing led to another, and before I knew it I was…I don't know. I couldn't even concentrate on the case, on anything. I'd never felt that way about anyone in my whole life. I guess I really haven't since. Then suddenly she was just…gone. She had to go away for her assignment, and I never saw her after that."

"Until today."

"Yeah."

"Well that explains it."

Charlie turned to his brother with a pained expression. "Don, I should be honest, I don't know if I can work on this case with her there."

"Come on, Charlie, I've got no choice about her helping! Besides, you can't always run away from these things, even if you want to. Trust me on that."

"You don't understand; it's…complicated."

"Complicated or not, you'll have to talk to her eventually."

"It's been so long; I wouldn't even have a clue where to start."

Don couldn't offer Charlie advice on this particular subject; it wasn't exactly his realm of expertise either. He started wondering how he hadn't heard about this woman before if they were so involved, and then something occurred to him.

"Three years ago…that was when mom got sick."

"Yeah, I know." Charlie turned back to the window.


	6. Chapter 6

_I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only._

_**Thank you all for your wonderful reviews! They recharge me when I think I'm too tired to write more!**_

**_A few notes on the Isabel thing: I know it's always a difficult thing with an original character, but I promise all will be revealed in time and you'll understand better why she does what she does. _**

**And now for the _real_ history!**

**-2002-**

Isabel sat in the car, waiting. She glanced at the clock on the dashboard. He was now 15 minutes late. This just wasn't like him. She'd give him five more minutes.

Five more minutes came and went and Isabel got out of the car. She looked up at his building, as though waiting for some sign of life from his window, but there was nothing. She would just have to go up and get him, assuming he was even there.

Upstairs, she knocked on the door to his office, which was standing ajar. When he didn't answer immediately, she pushed it open the rest of the way. Charlie was sitting in a chair in front of his blackboard, staring at it but clearly not seeing it.

"Charlie?"

No response.

"Charlie!"

He blinked slowly and turned his head slightly in her direction, but made no other indication he'd even heard her.

Isabel closed the door behind her and crossed the room to Charlie. She knelt down in front of him so that her face was level with his.

"Charlie, what's wrong?"

He only shook his head, but made no eye contact. She brought her hand softly to the side of his face, turning his to hers. His eyes finally brought her face into focus, and he seemed to snap back to reality suddenly.

"Oh, I'm late, we…" He started to get up from the chair, but she pushed him right back into it.

"Charlie, tell me what's wrong." She knew whatever was going on in his personal life was none of her business, but there was no way she was going to let him work in the state he was in.

As they sat there still, just staring at each other, Isabel saw Charlie's eyes begin to fill with tears. He slowly closed his eyes and let his head fall forward. Isabel brought her right hand up to his cheek and moved her thumb back and forth across it. "Charlie, whatever it is, you can tell me. We're friends, right?"

He turned his head slightly, letting more of its weight rest on her palm, but said nothing. He didn't know what to say and he didn't trust his voice not to break even if he tried. Isabel slid her hand around to the back of his neck and applied light pressure at a specific point, knowing it would release some tension. She looked down and saw that his pant legs were dotted with spots from his tears.

"Oh, Charlie…" His shoulders began to heave and she pulled him into a hug. She had no idea what was going on, but she'd never seen him so upset. Holding him against her, she felt a knot in her throat.

His voice was barely more audible than a whisper. "My mom, she's sick."

Isabel pulled herself away from Charlie enough to be able to see his face. His eyes were red and he had a mark on his forehead from pressing it into her shoulder. "I take it we're not talking about the flu."

Charlie shook his head. "Cancer."

Although Charlie felt some relief at having told someone, he knew it didn't change anything. His mind had been a blur since that morning when he found out. He should have known that something was wrong when Don showed up unexpectedly, but nothing could have prepared him for what it was. His mother was so calm about it, the way she just held their father's hand and explained the whole situation so matter-of-factly. As always, Don had seemed to know just what to say and do while Charlie just sat there. They were supposed to all go out to lunch together, but he couldn't do it. He'd mumbled some excuse about a big project and left. He was a horrible son, and he knew it.

Isabel didn't know what to say. She knew better than to tell him that everything would be all right. Her own mother had died when she was young, and although that had involved very different circumstances, she'd never put any value in empty promises. She brushed Charlie's curls out of his face. He hardly even looked like the same man she'd worked with yesterday. Yesterday's Charlie was confident, even cocky, and pulsing with energy, but this one looked broken and tired. It broke her heart to see him that way.

When she thought about it later, Isabel was unable to explain why she did what she did next. It was so out of character for her that she could hardly believe she did it. Bringing her hands up to his face, she slid them back into his hair, bringing his face closer to hers. Charlie seemed to realize at the last second what she was doing, but didn't pull away. She kissed him softly at first, but as Charlie responded in kind, it quickly became more passionate.

When they finally paused to catch their breath, their chests were heaving.

"Charlie?"

"Yeah?"

"Tell me to stop."

"I can't."

This time it was Charlie who leaned in first for the kiss, and there was nothing soft or slow about it. Just a minute ago he had felt as though something inside of him were dead. Now it felt like every cell in his body was suddenly on fire. In the back of his mind, he knew he shouldn't be kissing her, but she had started it, and he had no intention of being the one to stop it.

Isabel felt that her heart was beating so fast it might explode. She had been trained to control everything about her body—the speed of a kick, the strength of a punch, her breath, her heart rate, everything. She didn't know if she just couldn't control it right then or if she simply didn't want to. At this rate, the situation would quickly get out of control. This hadn't been her intention…or had it? She tore her lips away from his, but still kept her face dangerously close.

"Charlie, wait. We can't do this."

The wounded look on his face made her realize what she'd just said and suddenly she found she didn't care about being in control. "Here. I mean, we can't do this here."

His expression softened and he nodded slightly.

"My car is parked outside. I'll take you wherever you want to go."

"I just want to go with you."

"Okay." She moved her face the two inches it took to re-establish contact and kissed him softly. She stood up and offered her hand to help him up. He took it, and pulled her in for another kiss before she could turn for the door.

Somewhere in the back of her mind, she _knew_ it was wrong. He wasn't thinking clearly right now and part of her felt like maybe she was taking advantage. Yet the greater part was screaming at her how right this felt. She just desperately wanted to take away the pain that he was in, even if it was just for a little while.

Isabel pulled Charlie's arms off her waist and took two steps backward to the door, still holding his hands. "Come on, my place is about five minutes from here."

Charlie nodded, and stepped in close to her.

Before he could kiss her again, she brought her fingertips to his lips to stop him. "Please, Charlie, just think about this for a minute. I know what I'm doing, but you're hardly thinking clearly right now. I don't want you to do something you'll regret when your mind clears."

Charlie brushed his lips against her fingers and closed his eyes. "I know I may not be doing this for the right reason right now, but there's no way I'll regret it."

And he didn't.


	7. Chapter 7

_I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only._

_**Once again, thank you for all your great comments! Please keep reviewing! It's my fuel at this point!**_

**_----_**

_Back to present time where we last left off with Don & Charlie discussing Isabel in the solarium…_

The Eppes men were having a relatively quiet dinner until Don's cell phone rang.

"Eppes."

Don furrowed his brow as he listened to the caller. He pushed his chair back and got up as he spoke.

"We'll be right there."

Don snapped his phone shut and gave Charlie a meaningful look.

"We've got to go."

"Another bomb?" Charlie's stomach sank. It was late in the day; he thought they'd have at least until tomorrow before they'd have to deal with this again.

"Yeah, which means more data for you, so let's get going."

Alan looked worried. "You're taking him to the scene with you?"

"No, I'm dropping him off at the office on my way to the scene. Since he still can't drive," Don looked squarely at his brother, "this is how we have to do things."

Charlie let the comment go without any reaction. He was used to it by now. He ran upstairs to grab his things.

When he came back down, his father was standing at the foot of the stairs, a concerned look on his face. "Your brother's waiting outside in the truck. But before you go, I've got something to say."

"Dad, whatever it is, can't it wait?" Charlie knew Don was under enough stress already and didn't want to add to it by making them late.

"Look, I know this is very important and you're helping your brother Charlie, but I've never seen a case affect you this way. You need to learn when to take a break."

"Don't worry about it; I'm fine."

Alan gave his son a look that clearly indicated he didn't believe him. "You dragged yourself in here looking about as bad as I've seen you, Charlie! You hid upstairs until Don got here and you sulked all through dinner. I know you; you are not okay."

Outside, Don honked the horn.

"Look, dad, I've just had a long day. I've got a lot on my mind and it's not just this case. Don't worry about me. I have to go; I don't want to make Don late."

Alan stepped aside so Charlie could walk out. He watched his son leave; if anything, he was more worried about him than before.

Charlie slid into the passenger's seat, thankful that Don was on the phone and wouldn't have the chance to lecture him for taking so long.

"Right, no, I'll meet you there. I'm just dropping Charlie off first…What? Why? Fine. We'll talk about this when I get there. Bye."

"What's wrong?"

"Other than another bomb going off? Nothing—except maybe for you. Isabel's already at the site. Terry and David are there with her now."

Charlie stared out the window and sighed as they pulled out of their driveway. "I don't know how to do this, Don."

"Look, Charlie, I wish I could do the big brother thing and help you out here but I can't. I'm not any better at this stuff than you are. In good conscience I just couldn't give you any advice."

"I understand."

Don reached over and grabbed Charlie's shoulder, giving him a gentle squeeze. "You'll figure it out, buddy. You always do."

"Right." Charlie clearly didn't share his confidence.

"Look, let's just focus on the case right now. We both know how to do that." Somewhere in the back of his mind, Don realized that he shouldn't be encouraging Charlie to turn into the workaholic that he was. Yet at the same time, he knew he needed him to focus for the time being.

Charlie made a small sound of agreement as he stared out the window. "You know, this doesn't really fit the pattern, one of them going off this late."

"I know. It could mean a break for us. Maybe they made a mistake."

"Well, a mistake wouldn't necessarily work to our advantage—at least not for my work. It might just throw the data set off. I suppose I can at least put the location in and see what that gets us."

Don pulled the SUV up in front of the building to let Charlie out. "You work on that and call me if you come up with anything. Do you want to call Amita in to help you?"

"No, I've got it."

"Alright, later buddy."

"Bye, Don." Charlie grabbed his bag from the back seat and walked into the building as Don drove away. His mind was already buzzing with the new calculations, but at the same time it was thinking about Isabel. She'd always been able to do that—sneak into his thoughts when they were supposed to be on other things. He'd never been able to get used to it, and it certainly wasn't going to help him right now. He knew he had a long night ahead of him.

Don walked into the front lobby of the office building. Terry, David and Isabel were all standing near what had obviously been the origin of the blast.

"Sorry I'm late; what have we got so far?"

Terry looked quickly at David and Isabel before replying. "Well, we've got what looks to be our sixth bomb by this guy. Location fits, and at first glance so does the explosion, but we won't know until we run the full analysis. The bomb team already came and took what they needed. They said they'll call as soon as they have the results. The thing that doesn't fit is this." She made a gesture at the area around her. "All of the other bombs went off during the late morning or early afternoon hours when there were people present at the locations. No one is here in this building at this time of day. It doesn't fit."

"What do you think that means?"

"It's hard to say. If this was intentional, this suggests they're going backwards. Normally you'd expect to see this type of explosion first, and then it escalates into more populated sites, with the potential for more victims. It doesn't make sense, which leads me to believe that maybe this was just a mistake."

"That's what I was thinking. Hopefully the location data will still be enough to help Charlie with his equation."

Don looked over at Isabel, who was staring intently at him. "You've got another idea?" He knew his tone was a little more rude than normal, but he was tired and her presence right then was annoying him.

She regarded him carefully before speaking, as though she knew what he was thinking. "I was thinking that perhaps this isn't your bomber at all. I looked over the files and I think you're correct in your assumption that this person, or persons, is quite skilled. They don't seem apt to make 'mistakes.' Having a bomb go off at anything other than the predetermined time, or by their intended trigger, suggests sloppiness or inexperience. That leads me to believe that this is someone else's work. Someone else who thinks we'll assume this is the same bomber. This is the first scene I've looked at firsthand, but I can tell you from the photos of the other scenes that this doesn't fit."

Isabel had moved while she talked, walking the far perimeter of the lobby, outside of the blast radius. Don found himself getting more annoyed. Not because her reasoning hadn't made sense, but because the last thing he needed in his life, and especially his work, was another know-it-all to make him feel more inept at his own job. He was still annoyed that he'd had to consult her in the first place, and to top it all off, she was clearly going to be a distraction to Charlie.

After waiting a few more moments for her to elaborate, Don lost his patience. "And…?"

She didn't appear to realize he was addressing her and continued her slow walk around the room.

"Cruz! Were you going to expand on that line of thought?"

Isabel held her hand up to signal she needed a moment, but made no other comment. She disappeared from sight, dropping down behind the counter in the reception area.

Don shot Terry an exasperated look. She shrugged her shoulders, not knowing what to say. She could understand his frustration, but they needed all the help they could get.

Isabel's voice came from behind the counter. "David, you said we're the only ones left in this building, right?"

"Yeah." David turned around and looked warily at Terry and Don.

"Good. I don't like the looks of this."

"What's going on?" David started to walk toward the counter.

David's answer came in a string of expletives in a language he didn't understand. Isabel vaulted herself over the counter at the same time she screamed at them, "Get out!"

They didn't need to be told again. The four of them sprinted out the front doors. Terry was in the front and had just reached the sidewalk; she didn't even have time to react to the sound of the explosion as she was thrown to the pavement, the shattered glass showering down around her.


	8. Chapter 8

_I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only._

_**I apologize for the lengthy delay in getting this chapter to you. Real life is never interested in my writing schedule! Thanks for your patience and I will do my best to get future chapters up in a timelier manner!**_

_**Thanks for not giving up on this story and thanks again for all of your reviews!**_

**2002**

"You're going to get us busted, you know that?" Isabel smiled playfully at Charlie, who had just kissed and playfully bit the back of her neck.

"No one ever comes in here."

"That's hardly the point." She gave him the most serious look she could muster, hoping he'd take the hint.

He didn't.

The next time she looked up, he was staring at her intently and she knew _exactly_ what he was thinking. "Seriously, Charlie, I'm starting to think I've created a monster. What happened to my help here?" She held up a file folder and waved it around.

Charlie ran his hands through his hair and leaned back in his chair, looking up toward the ceiling. "I'm having a hard time concentrating."

"Look, I understand you have a lot on your mind, and our little…_escapades_…aren't helping. We still have to finish this, Charlie! You're going to get me into serious trouble at work. You don't want me to have to go get some other hot math genius to help me, do you?"

"There aren't any."

"Oh, so you think you're the only one, huh?" She lifted an eyebrow and did her best to hide her grin.

"The only genius? No. The only hot one? Yeah. And if you don't believe me you should come to my next conference with me."

"Pretty full of yourself, aren't you?"

"No, just pretty sure you're bluffing on replacing me."

"Well if you don't get to work, we're going to find out who's bluffing."

Charlie sat back in his chair and stared at the papers in front of him. They'd made significant progress since their start, but he also knew there was still plenty more to go. Normally he didn't have to try when it came to numbers, but lately he hadn't felt like himself. He wasn't joking when he told her he was having a difficult time concentrating. After five minutes of aimlessly shuffling papers, it was clear he wasn't getting back to work.

Isabel sighed, throwing down the folder and leaning back, arms crossed. "Are you stalling on purpose?"

Charlie looked up, surprised at the seriousness of her tone. "No."

"Then _please_ try to concentrate and help me get this done."

"So what happens exactly when we've finished this?" It was a question that had been nagging at him for weeks, but he'd been unwilling to ask it before now.

"It has to be put to the test out in the field." She leaned forward over the table again as she continued marking up the papers in front of her.

"Define 'out in the field'?"

"You know, the field—as in the real world. Out there." She pointed toward the window with her pen, but didn't take her eyes off her work.

"Are you going to be the one to test it?"

"Of course I am, Charlie, this is my assignment." Isabel didn't look up to see the concerned look on his face.

"Where are you going?"

Isabel finally looked up, an unreadable expression on her face. "You know I can't tell you that."

"How long will you be gone?" Charlie's mind was attempting to run through all of the various possibilities that their work could be used for and what it would entail, but at the same time he was distracted by the growing lump in his throat.

"You know I can't tell you that either—not only because it would be classified, but because honestly, I don't know."

"Days, weeks, months—what are we talking here?"

"Charlie, I don't know! Why are you asking me all of these questions right now; it's all moot until we finish this!"

"Maybe I don't want you to go…"

"You know I have to go. You've known that from the beginning. Please don't do this to me now." Isabel said the last few words in almost a whisper.

"What about what you're going to do to me?" The look on Charlie's face tore at Isabel. This was the conversation she always tried to steer them away from; no matter what, there would be no good outcome from it.

"Charlie, I promise we'll talk about this later, when we're alone."

"We're alone right now."

"We're working right now! Well, at least, one of us is!" Isabel gave Charlie a stern look. Maybe if she could get him back to work he'd drop the subject.

Charlie simply stared at her for a moment, then looked down and started shuffling through his notes again, a distant look on his face. This was the reaction that she hated. Though they'd only been together a short time, she liked to think she already knew him pretty well. This reaction meant he wouldn't be bringing this up again, but since that was what she wanted for the time being, she let it go.

Immersing herself in her work again, she jumped a little when her cell phone rang. She glanced at the number and felt her jaw clench before she answered it. "Diga."

Charlie glanced up from his papers when Isabel took the call. This was the second time since he got there that she'd taken a call in Spanish and although he didn't really know why, he didn't like it. It wasn't just that he had no clue what she was saying, and he knew she wouldn't tell him; it was feeling that something important was happening and he didn't know what it was.

He leaned forward and rested his head in his hands, trying to take slow, deep breaths. He swallowed, but it did nothing to get rid of the lump that was still persistently stuck in his throat. Isabel was speaking very rapidly; he had no hope of even picking out the few words he actually knew. He started to think about his mother. She'd had her 3rd doctor's appointment this week today. Somewhere in the back of his mind he knew he wasn't being a good son to her right now. He knew he should be spending more time with her instead of every waking hour at the office or at school. Somewhere in the farther recesses of his mind, he also recognized that he was simply trying to avoid the situation altogether, irrationally hoping that it would just go away if he did.

"Charlie?"

He looked up to see Isabel staring at him expectantly.

"Didn't you hear anything I just said?"

"Sorry, no."

Isabel frowned and crossed the room to where he was, sitting down on the edge of the table in front of him. She brushed his hair away from his face and ran her hand down his cheek and across the stubble on his jaw line. He rarely took the time to shave anymore.

As though reading his thoughts, she said, "Maybe you need to spend some time at home tonight."

"I know I probably should, but like you said, we need to get this done."

"This can wait until tomorrow."

"No. You just said we needed to get this done."

"It can wait for you; I can finish consolidating the data without you, you know."

"I don't want you to though."

"I know." She leaned over and kissed him on the forehead. Charlie closed his eyes and let out a deep breath. "Come on, I'll take you home."

"I don't want to go home."

"Well I'm not letting you stay here."

"Can't we just go somewhere?" He looked up at her with those deep eyes that always made her melt, but she knew that she couldn't give in this time.

"No, no more of that. I'm not going to be the rock you crawl under every time you want to hide from reality. Your family needs you and whether you realize it or not right now, you need them too."

"What I need is you."

"And I'll be here if you need me."

"But only for a limited time, right?" That look flashed in Charlie's eyes again, and Isabel felt the all-too-familiar pang of guilt again.

"Don't." She looked at the floor, unable to hold his gaze any longer.

Charlie stood up, taking his coat from the back of the chair. "I'll be at my house if you need me."

"I said I'll take you."

"No, thanks, I can get myself there."

"Charlie, please don't be angry with me. I don't have any control over this."

"I know; it's just work, right?"

He walked out the door and Isabel slid into the nearest chair, letting her head fall into her hands.


End file.
